From my U.S. Pat No. 4,215,297 issued July 29, 1980 and similar publications, it will be apparent that it is known to provide an electromagnetic hammer or other force-impulse tool in which an electromagnetic motor comprises an electromagnet coil adapted to attract an armature of magnetically permeable material so that the armature or magnetic mass, which can form part of a plunger or ram can generate an impact which is transmitted to a drill, chisel or other "bit" forming the working end of the tool.
The electromagnet is energized by an energy-storage element in the form of a capacitor or condenser which is charged through an inductor under the control of a first thyristor and which discharges to generate the electric current pulse of short duration within the coil to attract the armature and generate the percussive force on the percussion tool.
This discharge is controlled by a second thyristor and the gates or control electrodes of the two thyristors are connected to an electronic command circuit alternately triggering the thyristors by signal pulses alternately delivered thereto.
The mobile magnetic mass constituted by the armature plunger or ram can be suspended elastically and in this case, the spring suspension defines with a mobile mass a damped oscillating system. As will be developed below, when the electromagnetic impulse is applied out of synchronization with the movement of the magnetic mass, the force can be dissipated. However, when synchronization is provided, the force generated by the electromagnetic action can add to the force contributed by the oscillating system.
Thus it is important that the electrical impulses generated by the command circuit be in synchronization with the movement of the mobile mass.
It has been found to be difficult in the past to achieve this synchronization. For effective synchronization, for example, complex measuring and analytical circuitry and devices were required and, for example, oscilloscopes and the like were necessary.